Alfalfa Looper

Table of contents

Alfalfa Looper (Autographia Californica Speyer)

Identification and Life Cycle

There are usually two overlapping generations of alfalfa looper. The alfalfa looper adult, like the diamondback moth, is blown in from the U.S., although some may overwinter as pupae in the soil.

The adult moth's forewings are grey with a distinct yellow, sickle-shaped spot near the middle of each wing, while the body and hind wings are dull grey or brown. These moths appear all summer long due to overlapping generations. They feed on flower nectar at dusk and fly during daylight hours. Adults lay up to 150 to 200 yellow, hemispherical eggs, singly or in small groups on host plants prior to bloom, often near floral parts if present.

Larvae hatch in about a week and climb to the flowers and cut them off. As a result, patches of fields that showed bloom suddenly do not have any flowers. After four weeks of feeding, the larvae are mature and are about 25 mm (1") long. They are light green to olive green in colour, with a paler head, a light stripe down each side, and two light stripes along the back (Figure 4). The mature larvae appear to have a swollen abdomen. Mature larvae attach to plants and spin cocoons in which to pupate.

Photo by Roy Ellis

Damage

Infestations are not common but have occurred in northern and southern Alberta and parts of Manitoba. Damage is characterized by defoliation and clipping of flowers and small pods. Canola plants can recover from light damage. Alfalfa looper larvae are very susceptible to virus diseases that frequently and rapidly destroy populations of late-instar larvae. Unfortunately, in some cases, feeding damage is usually done before viral control can be effective.

Monitoring

Scout the field for larvae at the start of flowering. Look for characteristic clipping of flowers.

Economic Threshold

There is no economic threshold for alfalfa looper.

Management

Insecticides: If an infestation occurs, assess the damage and delay spraying as long as possible to allow diseases an opportunity to control the pest. Check provincial crop protection guides for registered insecticides.

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